In 2009, LoggerHead hit pay dirt when Sears agreed to do a test sale. The product sold out, Mr. Brown said, and Sears ordered 75,000 Bionic Wrenches the next year. In exchange Mr. Brown agreed not to sell the wrench to Sears’s competitors, including Home Depot and Lowe’s.

In 2011, sales at Sears increased again, far outpacing LoggerHead’s other outlets like the QVC shopping channel and smaller hardware stores. But LoggerHead’s profit margin remained small, in part because it produced a television commercial and paid Sears to show it.

The Sears Holdings Company, which owns the Craftsman brand, declined multiple requests to comment on the Bionic Wrench or the Max Axess Wrench. The company would not answer questions about patent infringement or the volume of sales.

But in a string of e-mails provided by Mr. Brown, the buyer at Sears who had the LoggerHead account wrote, making liberal use of exclamation points, that the wrench’s holiday sales last year exceeded its target by 23 percent.

In the manufacturing world, lead time can determine price, and from the beginning cost was a particular issue for the Bionic Wrench, because of the competition from China. A 2006 article in The Wall Street Journal was headlined, “Wrench Wins Awards, but Is It Priced Too High to Be a Hit?”

According to Mr. Brown’s account of his dealings with Sears, the chain was pleased with the tool’s performance and agreed to place an order for 2012 in plenty of time to keep the cost low. Then his buyer at Sears changed and that agreement seemed to get lost in a new round of haggling. When the order for Father’s Day finally came, Mr. Brown said, it was too late to guarantee the lower price. He refused the order.

Sears responded by agreeing to the higher price. But when it came time for the Christmas holiday order, negotiations stalled once more, again pushing LoggerHead past the deadline to get the best price, according to Mr. Brown.

“We were sitting there going, ‘Why do they want Father’s Day so bad but they won’t commit for Christmas?’ ” Mr. Brown said. Now he believes that the company had already placed its order for the Craftsman version.

In late September, Mr. Brown said, his suspicions were confirmed. LoggerHead got a “customer feedback” e-mail from Mr. Craig, the tool connoisseur, describing the new Max Axess wrenches. “Sadly, they are made in China,” Mr. Craig wrote. “Can you tell me if LoggerHead has authorized these?”

Craftsman has come under fire before, accused of misleading customers into thinking that its tools are made in America and for stealing intellectual property. In one case, Sears spent two decades defending itself against a claim by Peter M. Roberts, who as a young Sears employee had, on his own time, invented a type of socket wrench.

Mr. Roberts told the court that Sears had played down the value of his invention, paid him $10,000 for the rights, and then made tens of millions of dollars. He eventually received settlements of less than $10 million, according to news reports.

In another, more recent case led by Lee Grossman, Mr. Brown’s lawyer, a judge awarded $25 million to the maker of a tool called the Rotozip who said he had disclosed trade secrets to Sears in an attempt to get the store to carry a new version of the tool.

Sears, a jury decided, took the trade secrets and had the tool made abroad for Craftsman.

“You have LoggerHead out, Dan Brown out, and dozens of American workers laid off — all in the name of profits for Sears,” Mr. Grossman said.

LoggerHead’s lawsuit, Mr. Brown said, will most likely include claims that Sears interfered with the company’s ability to do business with other stores.

“I’m in favor of free trade,” Mr. Brown said. “The person who’s out-innovated loses. But it’s destructive when someone competes but doesn’t out-innovate, they just produce it in a different market without regard to safety codes and human conditions.”

The company that makes the Max Axess wrench and other tools for Craftsman, the Apex Tool Group, is being acquired by Bain Capital, the company founded by Mitt Romney, in a $1.6 billion deal.

Throughout the presidential campaign, Bain was criticized on the grounds that it encouraged outsourcing by companies it buys at the expense of American workers. Apex makes many of its tools overseas. A company spokesman referred all questions to Sears.

Mr. Brown and his lawyer say they believe they have a solid case against Sears, but it could take years to litigate. “What happens to us in the meantime?” Mr. Brown asked.

Mr. Brown is also concerned that while he fights in court, Sears can undercut the price of his wrench.

For now at least, Sears still has some of Mr. Brown’s wrenches in its inventory. On the Sears Web site, the Craftsman and the LoggerHead wrenches are listed at the same regular price, $24.99 for the 8-inch version, and today both are on sale. But for at least a few days in recent weeks, only the Craftsman version was on sale, for $19.99.